There are two basic things you consider in a good quality video.
First is the method of image presentation. With advancements in technology, you can already film like a pro in your smartphone and edit it in your phone and/or desktop. The video should have the proper lighting exposure, visually appealing, not shaky or free from irritating or annoying background noises. It should appear as smooth flowing, not abruptly cut, capturing in details what needs to be presented which words cannot just clearly express.
Second is the content presentation. Gone are the days when one had to be contented with silent pictures. Nowadays, a video cannot be complete with its storyline, characters, backed by other visual or sound effects. It must have an interesting story to tell or a product to promote, engaging enough to sustain attention and parting a message clearly understood by the audience.
The most challenging part is being able to produce an amazing work in a short time considering the short attention span. Just like a commercial, a video may last from 15-30seconds, less than 30minutes for vlogs.
Video is the "closest to reality" way of promoting. We cannot deny its great impart in building awareness and attracting positive or negative feedbacks from the market.